This invention relates generally to torque transmission systems, and specifically to lightweight transmission systems for use on rotorcraft, propeller-driven aircraft, and any other mechanically driven vehicle.
A torque transmission system transfers power from an engine or motor to driven components of a device or vehicle. In a rotorcraft or a propeller-driven aircraft, the proprotor transmission system transfers power from a turbine engine or other engine to the rotor or propeller of the rotorcraft or aircraft. A torque transmission system may direct power from one or more engines to a single driven component or to a number of driven components. The transmission system may also direct power to auxiliary systems. In a rotorcraft, a proprotor transmission system often directs power from two turbine engines to a single rotor, auxiliary systems, and a secondary rotor.
In many devices and vehicles, the rotational velocity of the driven component or components is significantly lower than the rotational velocity of the output of the driving engines or motors, thus the engine or motor rotational velocity must be reduced by the transmission system. In reducing the rotational velocity of the engine or motor output, torque is increased by the transmission system through a series of intermediate gear stages and shafts before final output to the driven component or components. In rotorcraft or propeller-driven aircraft, large gears are required near the final output of the proprotor transmission system to handle the high torque being supplied to the proprotor(s). A typical main rotor transmission housing these large gears is often the heaviest gear box in a rotorcraft.
Transmission size, weight, and reliability considerations, are important, especially in aircraft. Prior art transmissions typically power the auxiliary systems directly from the main transmission gears or by adding additional gearing to the main transmission system. This increases size, and adds weight and complexity.
FIG. 1 is a full cross-sectional view of a prior art concentric face gear transmission 10 for a rotorcraft. Power from a turbine engine (not shown) is transferred via an input clutch 20 to an input shaft 21. An input spur pinion 23, connected to the input shaft 21, is meshed between a lower face gear 25 and an upper face gear 30. The combination of the input shaft 21 and the input spur pinion 23 will be referred to herein as an input quill. A lower thrust bearing 27 for the lower face gear 25 is located radially inwardly of the lower face gear 25. An upper thrust bearing 32 for the upper face gear 30 is located radially outwardly of the upper face gear 30. Torque from the input shaft 21 is split between the lower face gear 25 and the upper face gear 30 at a single stage gear meshing 34.
The upper face gear 30 includes a web 36, connected to a female spline 38. The female spline 38 of the upper face gear 30 meshes with a male spline 41. The male spline 41 is connected to a sun gear 43. The sun gear 43 meshes with an inner radial portion of a planet gear 45. The planet gear 45, having an axis 47, rotates about the sun gear 43. An outer radial portion of the planet gear 45 meshes with a ring gear 49. The planet gears 45 are carried by a planet carrier 54, which rotates around a static support assembly 56. Power from the planet carrier 54 is used to drive the rotor of the aircraft through a main rotor drive shaft (not shown).
The cross section of FIG. 1 is taken through an input spur pinion 23 and an idler pinion 61. In the prior art transmission 10, the input spur pinion 23 is located opposite a second input spur pinion (not shown) and the idler pinion 61 is located opposite a second idler pinion (not shown).
The idler pinion 61 is connected to an idler shaft 60, which rotates around an axis that nearly intersects the axis of the static support assembly 56. The idler pinion 61 meshes with the lower face gear 25 and the upper face gear 30 at a single stage idler mesh 63. The idler pinion transfers and equalizes torque between the upper face gear 30 and the lower face gear 25.
In the prior art concentric face gear transmission 10 shown in FIG. 1, primary power torque from the first face gear stage of the transmission 10 is output from the upper face gear 30 through its web 36 and female spline 38. Auxiliary power is withdrawn from the transmission through the idler shaft 60, which is driven by the upper face gear 30 and lower face gear 25. The upper face gear 30 and the lower face gear 25 must carry the torque driving the auxiliary system together with the main power torque, necessitating heavier face gears. Also, the extraction of auxiliary power through the use of an idler pinion 61 and idler shaft 60 requires that the transmission housing and configuration be sized to accommodate larger idler components when they are utilized to drive auxiliary systems.
More generally, many forms of transmissions are often driven by input pinion or bevel gears on shafts, i.e. input quills, with auxiliary power extracted through additional gear components that mesh with the main transmission gears. For example, other prior art transmissions utilize input quills linked to bevel gears to drive secondary gearing in the transmission, without utilizing a face gear configuration. Alternately other prior art utilizes input pinion gears with single face gears, not utilizing concentric torque face gears. Examples of such transmissions are shown in FIGS. 1 and 2 of U.S. Pat. No. 5,802,918, Chen et al., Sep. 8, 1998. Independent of the configuration of the transmission, auxiliary power takeoffs for prior art transmissions as described herein, and other prior art, utilize the main power transmission system to drive the auxiliary power system, increasing its weight, and requiring the space and complexity of additional gearing within the main power system to drive the auxiliary power takeoffs.
Therefore, an unmet need exists for a transmission system which allows for auxiliary power takeoff without burdening the main transmission system with the weight, size, and complexity of the auxiliary power takeoff.
The present invention presents a hybrid input quill that presents a lightweight, compact, and uncomplicated system for driving auxiliary power takeoffs while driving a main transmission.
The hybrid input quill of the present invention includes at least one input pinion and one bevel pinion on a single input shaft allowing for two drive systems to be driven from the single hybrid input quill. The hybrid input quill may be incorporated into a concentric face gear transmission assembly where the input pinion gear drives the main power system of the device or vehicle, and the bevel gear drives auxiliary power systems. The bevel gear drives the auxiliary power system utilizing gearing outside of the primary power train reducing the weight, size, and complexity of the primary power train in the transmission.
According to an aspect of the invention, power is still transmitted to the auxiliary power system through the hybrid input quill when used in a multiengine configuration and the engine directly driving the hybrid input quill fails or is shut down. A clutch is utilized to disconnect the hybrid input quill from its input motor or engine, allowing the input quill to be driven by the balance of the transmission and other engine(s) or motor(s), providing extra safety or security in the drive system. The then-indirectly powered hybrid quill continues to drive its connected auxiliary system.
The invention provides flexibility for shimming, spacing, or otherwise locating the gearing systems for the primary power and auxiliary power takeoffs independently, to provide for optimum gear mesh configuration. Thus, the location of the bevel pinion may be shimmed or positioned separate from the input pinion. The input pinion and the bevel pinion may be independently positioned to obtain optimum gear meshing. The location of the input pinion assembly may be shimmed or positioned relative to the main transmission. Shimming of the shaft pinion separate from shimming of the bevel pinion permits both the shaft pinion. and the bevel pinion to be located optimally for their respective gearing systems.